TWI633677B - Metallization of solar cells using metal foils - Google Patents

Abstract

A solar cell structure includes P-type doped regions and N-type doped regions. Dielectric spacers are formed on the surface of the solar cell structure. The metal layer is formed on the surface of the dielectric spacer and the solar cell structure exposed by the dielectric spacer. The metal foil is placed on the metal layer. Use a laser beam to weld the metal foil to the metal layer. A laser beam is also used to pattern the metal foil. The laser beam erodes the metal foil and metal layer on the dielectric spacer. Laser ablation of metal foil cuts the metal foil into separate P-type metal fingers and N-type metal fingers.

Description

Metallization of solar cells using metal foil

The embodiments of the patent subject matter described herein generally relate to a solar cell. More specifically, the embodiments of the patent subject matter relate to a manufacturing process and structure of a solar cell.

Solar cells are conventional devices used to convert solar radiation into electrical energy. The solar cell has a front side facing the sun to collect solar radiation during normal operation and a back side opposite to the front side. The solar radiation impinging on the solar cell generates a charge that can be used to power an external circuit, such as a load. The external circuit may receive current from the solar cell through a metal finger connected to the doped region of the solar cell.

In one embodiment of the present invention, a method for preparing a solar cell is disclosed. The method includes: forming a dielectric spacer on the surface of the solar cell structure; forming a metal layer on the dielectric spacer, the N-type doped region and the P-type doped region, wherein the metal layer is electrically connected to the N-type Doped region to P-type doped region; in metal Metal foil is placed on the layer; and after the metal foil is placed on the metal layer, the metal foil is patterned, wherein the patterned metal foil includes a portion of the metal foil and the metal layer removed on the dielectric spacer.

In yet another embodiment of the present invention, a solar cell structure is disclosed. The solar cell structure includes N-type doped regions and P-type doped regions; dielectric spacers located on N-type doped regions and P-type doped regions; On the first metal layer, wherein the first metal layer is electrically connected to the N-type doped region; the second metal layer on the dielectric spacer and the P-type doped region, wherein the second metal layer is electrically Connected to the P-type doped region; first metal foil fingers electrically bonded to the first metal layer; and second metal foil fingers electrically bonded to the second metal layer.

In still another embodiment of the present invention, a method for preparing a solar cell is disclosed. The method includes forming a dielectric spacer on the surface of the solar cell structure; depositing a metal layer on a portion of the surface of the solar cell structure exposed by the dielectric spacer; mounting the metal foil to the metal layer; and mounting the metal foil After the metal layer, the metal foil is patterned.

In one embodiment, dielectric spacers are formed on the surface of the solar cell structure. The metal layer is formed on the dielectric spacer and on the surface of the solar cell structure exposed by the dielectric spacer. The metal foil is placed on the metal layer. Use a laser beam to weld the metal foil to the metal layer. A laser beam is also used to pattern the metal foil. The laser beam ablate parts of the metal foil and metal layer on the dielectric spacer. Laser ablation of metal foil cuts the metal foil into separate P-type metal fingers and N-type metal fingers.

These and other features of the present disclosure to those of ordinary skill in the art by referring to the full text of the present disclosure, which includes drawings and patent application scope, It's easier to see.

100‧‧‧Solar battery structure

101‧‧‧Solar cell substrate

103‧‧‧Dielectric spacer

104‧‧‧Metal layer

105、105A‧‧‧Metal foil

106‧‧‧welding contact

107‧‧‧Cutting

108, 109‧‧‧ metal finger

201, 202, 203, 204, 205‧‧‧ steps

When considering the following drawings, a more complete understanding of the patentable subject matter can be derived by referring to the detailed description and the scope of the patent application, wherein the same reference symbols represent similar elements throughout the drawings. The drawing is not to scale.

FIGS. 1 to 7 are cross-sectional views schematically illustrating a method of manufacturing a solar cell according to an embodiment of the present disclosure.

FIG. 8 is a plan view of an unpatterned metal foil according to an embodiment of the present disclosure.

FIG. 9 is a plan view of the metal foil of FIG. 8 after patterning according to an embodiment of the present disclosure.

FIG. 10 is a flowchart of a method of manufacturing a solar cell according to an embodiment of the present disclosure.

FIG. 11 and FIG. 12 are schematic cross-sectional views schematically showing a patterned metal foil at a module level according to an embodiment of the present disclosure.

13 and 14 are cross-sectional views schematically illustrating the use of a metal foil with a patterned metal layer according to an embodiment of the present disclosure.

The following detailed description is merely illustrative in nature and is not intended to limit the patented embodiments or the application and use of such embodiments. As used in this article, the text "exemplary" means "as an example, Instance (instance) or illustration (illustration) ". Any exemplary embodiments described herein need not be interpreted as being better or better than other embodiments. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, summary or the following embodiments.

This specification includes references to "one embodiment" or "an embodiment." The expression "in one embodiment" or "in an embodiment" does not necessarily mean the same embodiment. Special features, structures, or characteristics may be combined in any suitable manner consistent with the present disclosure.

In this disclosure, many specific details are provided, such as structure and method embodiments, to provide a thorough understanding of the embodiments. However, those of ordinary skill in the art will recognize that embodiments can be implemented without one or more specific details. In other instances, conventional details are not shown or described to avoid obscuring the appearance of the embodiments.

FIGS. 1 to 7 are cross-sectional views schematically illustrating a method of manufacturing a solar cell according to an embodiment of the present disclosure. The prepared solar cell is an all back contact solar cell, wherein the N-type doped region and the P-type doped region and the metal coupled to the N-type doped region and the P-type doped region refer to On the back of the solar cell.

Referring first to FIG. 1, a solar cell structure 100 according to an embodiment of the present disclosure is shown. In the embodiment of FIG. 1, the solar cell structure 100 includes a plurality of alternating N-type doped regions and P-type doped regions that can be formed in the solar cell substrate 101 or outside the solar cell substrate 101. For example, the N-type doped region and the P-type doped region can be diffused into the solar energy by N-type dopant and P-type dopant, respectively. The battery substrate 101 is formed. In another embodiment, the N-type doped region and the P-type doped region are formed in a separate layer of material such as polysilicon formed on the solar cell substrate 101. In this embodiment, N-type dopants and P-type dopants are diffused into polysilicon (which may or may not be trench) to form N-type doping in polysilicon rather than in solar cell substrate 101 Region and P-type doped region. The solar cell substrate 101 may include, for example, a monocrystalline silicon wafer.

In the embodiment of FIG. 1, the symbols “N” and “P” schematically represent N-type doped regions and P-type doped regions or are electrically connected to the N-type doped regions and the P-type doped regions. More specifically, the reference "N" schematically represents the exposed N-type doped region or the exposed metal connection to the N-type doped region. Similarly, the reference "P" schematically represents the exposed P-type doped region or the exposed metal connection to the P-type doped region. The solar cell structure 100 may therefore represent after the formation of the contact holes connected to the N-type doped region and the P-type doped region, but the metal contact used to form the N-type doped region and the P-type doped region The structure of the solar cell prepared before the metallization process.

In the embodiment of FIG. 1, the N-type doped region and the P-type doped region are on the back of the solar cell structure 100. The back side of the solar cell structure 100 is opposite to the front side directly facing the sun to collect solar radiation during normal operation.

Next, referring to FIG. 2, a plurality of dielectric spacers 103 are formed on the surface of the solar cell structure 100. In the embodiment of FIG. 2, the dielectric spacer 103 is formed on a region on the surface of the solar cell structure 100 on the interface between adjacent P-type doped regions and N-type doped regions. As can be understood, the dielectric spacer 103 may also be formed on other regions according to the details of the solar cell structure 100.

In one embodiment, the dielectric spacer 103 is printed on the solar cell structure 100 by screen printing. The dielectric spacer 103 can also be formed using other dielectric forming processes, including by spin coating and by deposition (eg, chemical vapor deposition) followed by patterning (eg, masking and etching) . The dielectric spacer 103 may include a dielectric material with an optical absorber, a fireable dieletric, and the like. As a specific example, the dielectric spacer 103 may include polyimide (eg, with a titanium oxide filter) screen-printed on the solar cell structure 100 to a thickness of 1-10 microns. In general, the dielectric spacer 103 may be configured to have a thickness and composition that will block (for example, by absorption or reflection) the laser beam used in the patterning of the metal foil 105 (see FIG. 5), It is compatible with the process used to form an overlapping metal layer (eg, metal layer 104 in FIG. 3).

In the embodiment of FIG. 2, each dielectric spacer 103 is formed on the N-type doped region and the P-type doped region of the solar cell structure 100. As is more obvious below, in the subsequent metallization process, the metal foil is patterned using laser when the metal foil is on the solar cell structure 100. The dielectric spacer 103 advantageously blocks the laser beam that can penetrate into the solar cell structure 100 during the patterning of the metal foil 105.

As shown in FIG. 3, the metal layer 104 is formed on the solar cell structure 100. The metal layer 104 provides electrical connection to the N-type doped region and the P-type doped region to subsequently form metal fingers. In one embodiment, the metal layer 104 includes a conformal continuous blanket metal coating on the dielectric spacer 103. For example, the metal layer 104 may be formed on the dielectric spacer 103, the N-type doped region, and the P-type doped region by sputtering, deposition, or some other process to form 10 Angstroms to 5 microns (eg, 0.3 micro Meters to 1 micron) of aluminum. In general, the metal layer 104 includes a material that can be bonded to the metal foil 105. For example, the metal layer 104 may include aluminum to facilitate welding to the aluminum metal foil 105. In FIG. 3, the metal layer 104 is still electrically connected to the N-type doped region to the P-type doped region. The metal layer 104 is then patterned during the patterning of the metal foil 105 to separate the N-type doped regions from the P-type doped regions.

Referring next to FIG. 4, the metal foil 105 is roughly placed on the solar cell structure 100. The metal foil 105 is a "metal foil", which contains a metal sheet prepared in advance. FIG. 8 is a plan view of the metal foil 105 at this stage of the manufacturing process. As shown in Fig. 8, the metal foil 105 is not patterned. As will be more apparent below, after the metal foil 105 is mounted to the metal layer 104, the metal foil 105 is subsequently patterned to form the metal fingers of the solar cell.

Next, in FIG. 5, the metal foil 105 is placed on the solar cell structure 100. Unlike the metal deposited or coated on the solar cell structure 100, the metal foil 105 is a plate prepared in advance. In one embodiment, the metal foil 105 includes an aluminum plate. The metal foil 105 is placed on the solar cell structure 100 where it is not formed on the solar cell structure 100. In one embodiment, the metal foil 105 is placed on the solar cell structure 100 by being mounted to the metal layer 104. The installation process may include squeezing the metal foil 105 to the metal layer 104 so that the metal foil 105 is in close contact with the metal layer 104. The installation process may cause the metal foil 105 to be conformal on the features (eg, bumps) of the metal layer 104. A vacuum may be used to squeeze the metal foil 105 against the metal layer 104 to obtain a gap of less than 10 microns between them during welding. It is also possible to press the metal foil 105 against the metal layer 104 using a pressing plate during welding; the pressing plate is removed for laser ablation.

FIG. 6 shows the solar cell structure 100 after the metal foil 105 is electrically bonded to the metal layer 104. In the embodiment of FIG. 6, when the metal foil 105 is pressed against the metal layer 104, the metal foil 105 is directed onto the metal foil 105 by the guided laser beam While welding to the metal layer 104. The laser welding process produces solder joints 106 that electrically connect the metal foil 105 to the metal layer 104. Because the metal foil 105 is not patterned at this stage of the manufacturing process, the metal foil 105 is still electrically connected to the N-type doped region and the P-type doped region of the solar cell structure 100.

Next in FIG. 7, the metal foil 105 is patterned to form metal fingers 108 and metal fingers 109. In one embodiment, the metal foil 105 is patterned by ablating portions of the metal foil 105 and the metal layer 104 on the dielectric spacer 103. The metal foil 105 and the metal layer 104 can be ablated using a laser beam. The laser ablation process can cut (see 107) the metal foil 105 into at least two separate pieces, one piece is a metal finger 108 electrically connected to the N-type doped region and the other piece is electrically connected to the P-type The metal finger 109 of the doped region. The laser ablation process interrupts the electrical connection between the N-type doped region and the P-type doped region through the metal layer 104 and the metal foil 105. The metal foil 105 and the metal layer 104 are thus patterned in the same step, which advantageously reduces the manufacturing cost.

FIG. 9 is a plan view of the patterned metal foil 105 of FIG. 7 according to an embodiment of the present disclosure. FIG. 9 shows that the cutting 107 physically separates the metal finger 108 from the metal finger 109. In the embodiment of FIG. 9, the metal foil 105 is patterned to form interdigitated metal fingers 108 and interdigitated metal fingers 109. Other metal finger designs can also be used depending on the solar cell.

Returning to FIG. 7, the laser ablation process uses a laser beam that gradually cuts the metal foil 105 and the metal layer 104. According to the process window of the laser ablation process, the laser beam can also cut its part, but does not pass through the dielectric spacer 103. The dielectric spacer 103 advantageously blocks the laser beam that can be reached and damages the solar cell structure 100 in other ways. The dielectric spacer 103 also advantageously protects the solar cell structure 100 from mechanical damage, such as during the installation of the metal foil 105 to the metal layer 104. Dielectric spacer 103 is completing Can be left in the solar cell, so its use does not need to involve a removal step added after the patterning of the metal foil 105.

In view of the foregoing, those of ordinary skill in the art will understand that the embodiments of the present disclosure provide additional benefits that have not been realized so far. The use of metal foil to form metal fingers is relatively cost-effective compared to metallization processes that involve the deposition or plating of metal fingers. The dielectric spacer 103 allows the laser welding process and the laser ablation process to be performed in situ, that is, successively on the same process station. The dielectric spacer 103 also enables the use of laser beams to pattern the metal foil 105 when the metal foil 105 is on the solar cell structure 100. As can be understood, it is easier to place and align the metal foil plate than to place and align the individual strips of metal fingers, with precision on the micrometer scale. Unlike etching and other chemically-based patterning processes, the use of laser to pattern metal foil 105 reduces the amount of residue that may be formed on the prepared solar cell.

It is further noted that in the embodiment of FIG. 9, the metal layer 104 and the metal foil 105 are simultaneously patterned. This advantageously eliminates unnecessary steps for patterning the metal layer 104 to separate the P-type doped region and the N-type doped region before laser welding and ablation.

FIG. 10 shows a flowchart of a method of manufacturing a solar cell according to an embodiment of the present disclosure. The method of FIG. 10 can be performed on a solar cell structure having N-type doped regions and P-type doped regions. The method of FIG. 10 may be performed at the cell level during the preparation of the solar cell or at the module level when the solar cell is connected and packaged with other solar cells. Note that in various embodiments, the method of FIG. 10 may include more or fewer blocks than shown.

In the method of FIG. 10, a plurality of dielectric spacers are formed on the surface of the solar cell structure (step 201). Each dielectric spacer may be formed on the N-type doped region and the P-type doped region of the solar cell structure. The dielectric spacer may be formed by screen printing, spin coating, or by deposition and patterning, for example. The metal layer is thereafter formed on the dielectric spacers and exposed on the surface of the solar cell structure between the dielectric spacers (step 202). In one embodiment, the metal layer is a continuous and conformal layer formed by blanket deposition. The metal foil is mounted to the metal layer (step 203). In one embodiment, the metal foil is welded to the metal layer using a laser beam (step 204). Note that non-laser based welding techniques can also be used to weld the metal foil to the metal layer. A laser beam can also be used to ablate the metal foil and metal layer portions on the dielectric spacer (step 205). The laser ablation process is to pattern the metal foil into separate metal fingers, and pattern the metal layer to separate the P-type doped region and the N-type doped region.

When the manufactured solar cell is packaged with other solar cells, the metal foil 105 can be patterned at the module level. In this embodiment, the metal foil 105 can be mounted to the metal layers 104 of the plurality of solar cell structures 100. This is schematically shown in FIG. 11 in which the metal foil 105A is mounted to the metal layer 104 of two or more solar cell structures 100. The metal foil 105A is the same as the metal foil 105 previously discussed except that the metal foil 105A spans more than one solar cell structure 100. As shown in FIG. 12, the metal foil 105A can be patterned by laser ablation when it is on the solar cell structure 100. The laser ablation process can pattern the metal foil 105A into metal fingers 108 and metal fingers 109 as previously discussed. After patterning, the metal foil 105A may be cut to physically separate the solar cell structure 100. After patterning, a portion of the metal foil 105A may also be left in place to string adjacent solar cell structures 100 together.

In one embodiment, the laser ablation of the metal foil 105A retains the adjacent The connection between the opposite metal fingers of the solar cell structure 100. This is the embodiment shown schematically in FIG. 12, in which the metal foil 105 is patterned so that the P-type metal fingers 109 of one solar cell structure 100 retain the N-type metal connected to the adjacent solar cell structure 100 Refers to 108 to electrically connect the solar cell structure 100 in series. Because the patterning of the metal foil 105A can be combined with the solar cell structure 100 in series, this advantageously saves the preparation steps at the module level.

As explained, the metal layer 104 may form a cap layer that is a metal that electrically connects the P-type doped region and the N-type doped region, and is then patterned to separate the P-type doped region and during patterning of the metal foil 105 N-type doped region. In other embodiments, according to the details of the manufacturing process, the metal layer 104 may be patterned before laser welding and ablation. This is schematically shown in FIG. 13 in which the metal layer 104 is formed on the P-type doped region and the N-type doped region which are not electrically connected. For example, the metal layer 104 may be deposited on the dielectric spacer 103, the N-type doped region, and the P-type doped region by overlay deposition, and then patterned as shown in FIG. 13 (eg, via Masking and etching) to separate N-type doped regions from P-type doped regions. As previously described, the metal foil 105 can then be placed on the patterned metal layer 104 and the dielectric spacer 103, laser welded to the metal layer 104, and patterned by laser ablation. FIG. 14 schematically shows the N-type metal fingers 108 and the P-type metal fingers 109 after the laser ablation process in this embodiment. The laser ablation process is cut through the metal foil 105 but terminated at the dielectric spacer 103.

The method and structure for preparing solar cells are disclosed. Although specific embodiments are provided, it is understood that these embodiments are for descriptive purposes and not limiting. Many additional embodiments will be apparent to those of ordinary skill in the art after referring to this disclosure.

The scope of this disclosure includes any features or groups of features disclosed herein Together (obviously or implicitly) or any of its general rules, regardless of whether it alleviates any or all of the problems addressed in this article. Accordingly, during the examination of this application (or this application claiming priority), any such combination of features can be used to formulate a new patent application scope. In particular, referring to the scope of the attached patent application, the features of the dependent items can be combined with the features of the independent items and the features of the individual items can be combined in any suitable way and not just the specific combinations listed in the appended patent application .

Claims (17)

A method for preparing a solar cell, the method comprising: forming a dielectric spacer on a surface of a solar cell structure; forming on the dielectric spacer, an N-type doped region and a P-type doped region A metal layer, wherein the metal layer electrically connects the N-type doped region to the P-type doped region; placing a metal foil on the metal layer; and after placing the metal foil on the metal layer, patterning the Metal foil, wherein patterning the metal foil includes removing portions of the metal foil and the metal layer on the dielectric spacer, and wherein the method further includes welding the metal foil to the metal layer. The method as described in item 1 of the patent application scope, wherein patterning the metal foil includes directing a laser beam on the metal foil to ablate the metal foil. The method as described in item 2 of the patent application range, wherein the laser beam also ablate at least a portion of the dielectric spacer below the metal layer. The method as described in item 1 of the patent application scope further includes: welding the metal foil to the metal layer by guiding a laser beam on the metal foil. The method as described in item 1 of the patent application range, wherein the metal layer is formed on the dielectric spacer by overlay deposition. The method as described in item 1 of the patent application scope, wherein the metal foil is patterned into a P-type metal finger and an N-type metal finger, and the P-type metal finger is physically and electrically derived from the N-type metal finger Separate. The method as described in item 1 of the patent application scope, wherein the metal foil is placed on the metal layer of the solar cell structure and another metal layer of another solar cell structure. The method as recited in item 7 of the patent application range, wherein patterning the metal foil includes retaining electrical connections between the metal fingers of the solar cell structure and the another solar cell structure. A solar cell structure includes: an N-type doped region and a P-type doped region; a dielectric spacer on the N-type doped region and the P-type doped region; a first metal layer , On the dielectric spacer and the N-type doped region, wherein the first metal layer is electrically connected to the N-type doped region; a second metal layer, on the dielectric spacer and the On the P-type doped region, wherein the second metal layer is electrically connected to the P-type doped region; a first metal foil finger is electrically bonded to the first metal layer; a second metal foil finger, It is electrically connected to the second metal layer; and a soldering joint connects the first metal foil finger to the first metal layer and connects the second metal foil finger to the second metal layer. The solar cell structure as described in item 9 of the patent application scope, wherein the solar cell includes a full back contact solar cell. The solar cell structure as described in item 9 of the patent application range, wherein the first metal foil finger and the second metal foil finger include aluminum. A method of preparing a solar cell, the method comprising: forming a dielectric spacer on a surface of a solar cell structure; depositing a on a portion of the surface of the solar cell structure exposed by the dielectric spacer Metal layer; mounting a metal foil to the metal layer; patterning the metal foil after installing the metal foil to the metal layer; and welding the metal after mounting the metal foil to the metal layer but before patterning the metal foil Foil to the metal layer. The method as described in item 12 of the patent application range, wherein mounting the metal foil to the metal layer includes placing an aluminum foil plate on the metal layer. The method as described in item 12 of the patent application range, wherein patterning the metal foil includes directing a laser beam on the metal foil to ablate the metal foil and the metal layer. The method of item 12 of the scope of the patent application, wherein depositing the metal layer on the dielectric spacer comprises depositing a metal capping layer on the dielectric spacer. The method as described in item 12 of the patent application range, wherein forming the dielectric spacer on the surface of the solar cell structure comprises printing the dielectric spacer on the surface of the solar cell structure. The method as described in item 12 of the patent application scope, further comprising: after mounting the metal foil to the metal layer but before patterning the metal foil, directing a laser beam on the metal foil to weld the metal foil To the metal layer.